1. Field of the Invention
The present invention relates to a process for the conversion of hydrocarbons. More particularly, this invention relates to a catalytic process for the isomerization of saturated aliphatic hydrocarbons.
2. Description of the Prior Art
It is known that aliphatic hydrocarbons can be isomerized in processes involving the use of a metal halide catalyst and a hydrogen halide in the presence or absence of hydrogen. Furthermore, it is known that isomerization can be conducted below the critical temperature of the hydrogen halide at substantially liquid phase conditions.
German patent No. 764,704 discloses that it is beneficial to use at least 100 weight percent of hydrogen halide to hydrocarbon feed in the isomerization zone to suppress cracking. It further discloses that temperatures in the range of 50.degree. to 150.degree.C may be used.
U.S. Pat. No. 2,250,410 discloses an isomerization process conducted in the presence of a metal halide catalyst at a temperature of 20.degree. to 150.degree.C under a superatmospheric pressure, the total pressure in the system being sufficiently high to insure the presence of a liquid phase of hydrocarbon in the system and the partial pressure of a hydrogen halide in the system being equivalent to 3 to 20 atmospheres when measured at 20.degree.C.
U.S. Pat. No. 2,271,043 discloses an isomerization which may be conducted in liquid or gaseous phase at a temperature below 200.degree.C in the presence of a hydrogen halide promoter and between 0.08 and 33 atmospheres of added hydrogen to repress undesired side reactions.
It has now been found that superior isomerization results can be obtained when the isomerization is conducted at pressure and temperature conditions comprised within the area (with reference to a pressure-temperature plot) bounded by the loci of the critical constants of mixtures of the hydrogen halide and hydrocarbon feed, at a specified ratio of hydrogen halide to metal halide catalyst, in the presence of added hydrogen.